The objective of this study was to assess the effect of antiandrogen on the activation of mutated androgen receptor (AR) and its signaling pathway in prostate cancer. We transfected the AR gene with a point mutation at codon 741 (tryptophan to leucine; W741L) into human androgen-independent prostate cancer PC3 cells lacking the expression of AR, and established PC3 cells overexpressing mutant type AR (PC3/W741L). Changes in the phenotype in these cells were compared to those in PC3 cells transfected with wild- type AR (PC3/Wild) and control vector alone (PC3/Co). There was no significant differences in the growth among PC3/Co, PC3/Wild and PC3/W741L cells. A transactivation assay using these cells showed that bicalutamide activated W741L mutant type AR, but not wild-type AR, while hydroxyflutamide failed to activate either type of ARs. Treatment with specific inhibitors of the MAPK or STST3 pathway (UO126 or AG490, respectively), in contrast to treatment with the Akt pathway inhibitor LY294002, significantly inhibited the dihydrotestosterone-induced activation of both wild-type and mutant ARs; however, activation of W741L mutant AR by bicalutamide was significantly inhibited by treatment with UO126, in contrast to treatment with AG490 or LY294002. Furthermore, treatment of PC3/W741L with bicalutamide, in contrast to treatment with hydroxyflutamide, resulted in significant upregulation of phosphorylated p44/42 MAPK. These findings suggest that the MAPK pathway might be involved in the activation of the AR with a point mutation at codon 741 induced by treatment with the antiandrogen bicalutamide.

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